What is the parameter order of a quaternion constructor?
You can figure it out easily in the py console:

q = Quaternion((1,2,3,4))
print(q.w, q.x, q.y, q.z)
# -&gt; 1.0 2.0 3.0 4.0, so it's WXYZ


The mathutils module is not python source btw., the Quaternion class is written in C and located here:


  BlenderSVN\blender\source\blender\python\mathutils\mathutils_Quaternion.c